Hearing aids are hearing devices that can be worn and which are used to assist those with impaired hearing. Different types of hearing aids, such as behind-the-ear (BTE) hearing aids, hearing aids with an external receiver (RIC: receiver in the canal) and in-the-ear (ITE) hearing aids, e.g. also concha hearing aids or completely in the canal hearing aids (ITE, CIC), are available to meet the numerous individual needs. The hearing aids listed by way of example are worn on the outside of the ear or in the auditory canal. Bone conduction hearing aids and implantable or vibrotactile hearing aids are also commercially available. With these the impaired hearing is stimulated either mechanically or electrically.
The essential components of a hearing aid are in principle an input transducer, an amplifier and an output transducer. The input transducer is generally a sound receiver, e.g. a microphone, and/or an electromagnetic receiver, e.g. an induction coil. The output transducer is generally in the form of an electroacoustic transducer, e.g. a miniature loudspeaker, or as an electromechanical transducer, e.g. a bone conduction earpiece. The amplifier is generally incorporated in a signal processing unit. This basic structure is shown in FIG. 1 using the example of a behind-the-ear hearing aid. One or more microphones 2 for receiving ambient sound are incorporated in a hearing aid housing 1 to be worn behind the ear. A signal processing unit 3, which is likewise incorporated in the hearing aid housing 1, processes and amplifies the microphone signals. The output signal of the signal processing unit 3 is transmitted to a loudspeaker or earpiece 4, which outputs an acoustic signal. In some instances the sound is transmitted by way of a sound tube, which is fixed in the auditory canal with an otoplastic, to the eardrum of the hearing aid wearer. Power is supplied to the hearing aid and in particular to the signal processing unit 3 by way of a battery 5 likewise incorporated in the hearing aid housing 1.